The present invention relates to foam-in-place packaging of articles susceptible to damage during handling, shipment and storage and in particular, relates to foam-in-bag packaging systems which will produce foam cushions upon demand and a method of producing the same.
The packaging of fragile articles or articles susceptible to damage during such packaging, shipment and storage presents many distinct problems. Foam-in-place packaging has been well known and widely used as protective packaging for such articles for a number of years. Foam-in-place technology is based upon the reaction between two (usually liquid) precursor components, which when mixed will react to form a polymer foam and gaseous by-products. In particular, and most commonly, an isocyanate containing component is mixed with a polyol containing component and these components react to produce a urethane polymer (polyurethane), steam and carbon dioxide. Under proper conditions, the steam and carbon dioxide generated by the reaction will disburse through the polymer and form an expanded polyurethane foam that provides protective cushioning for articles being packaged. The reaction of the components, when mixed to form an expanded foam, takes a minute or two and this time frame makes it feasible to manipulate and use the foam for packaging purposes. Initially, the foam precursor components were injected into containers (e.g. corrugated boxes), and either a mold element was used to form an article receiving cavity as the foam expanded or the article wrapped in a protective material was itself placed in the container and the foam permitted to expand therearound. Such foam-in-place packaging has been very successful and is still widely used for certain packaging purposes. However, such foam-in-place packaging did not address or was not suited for many packaging purposes.
Accordingly, a next generation of foam-in-place packaging has been developed in which devices were provided which concurrently form plastic bags and inject into the bag the mixture of foam precursor components. This bag is provided with vents to the outside to permit the steam and carbon dioxide by-products to escape during the formation of the foam. Prior to the reaction of the components to produce foam, an operator places the newly made bag into a container in which an object has been placed and then closes the container. The precursors react to produce foam which fills the void areas within the container, while forming a custom shaped cushion around the object being packaged. Such foam-in-bag packaging technology has also been quite successful and is now in substantial use.
Examples of such foam-in-bag technology heretofore developed is shown and described in a number of patents commonly assigned with this application and including U.S. Pat. Nos. 4,800,708; 4,854,109; 4,938,007; 5,027,583; 5,139,151 and 5,376,219.
All of these devices are characterized by forming the bags and injecting the foam precursor components into the bags immediately prior to the reaction of the components and the production of foam in the bags. Therefore, these devices by necessity must be placed adjacent the packaging operation. Here again, these devices are not adaptable or usable in all packaging situations, although they have greatly expanded the use of foam-in-place packaging technology.
U.S. Pat. No. 5,699,902, also commonly assigned to the Assignee of this application, discloses a still further generation of foam-in-place packaging. This patent discloses a packaging system in which a bag is formed of flexible plastic film material defining an enclosed space therein and having separate interior cells in the enclosed space. The cells contain two different foam precursor components. The two cells containing the foam precursor components are separated by a frangible seal which maintains the precursor components separate until it is desired to use the bag. Once the packaging system is to be used, the frangible seal between the two cells is broken and the two precursor components are mixed.
There is also provided another frangible seal between the cells and the enclosed space within the bag. This second frangible seal is broken by the reaction of the two precursor components and the production of foam which expands out of the cells into the enclosed space in the bag until the interior of the bag is substantially filled and a foam cushion is formed. The interior of the bag is vented to the outside so that the gaseous by-products of the foaming reaction may escape from the bag. By this arrangement, a foam-in-bag packaging system has been provided in which bags could be produced at locations remote from the packaging operations, packaged in containers, shipped to the packaging operation locations and stored until desired for use. When desired for use, an appropriately sized bag is removed from its container, the first frangible seal between the two cells is broken and the chemicals mixed, and the second frangible seal is broken by the reaction and a foam cushion is formed in the enclosed space in the bag. Accordingly, a packaging system of greatly increased versatility and usability was thus provided. However, the production of reliable frangible seals which maintain the two components separate, but which may be readily fractured to permit mixing of the components has been the cause of concern and anxiety.
With the foregoing in mind, it is an object of the present invention to provide flexible packages having a unique frangible seal which maintains precursor components separate while being readily fracturable upon desired use of the package to provide mixing of the heretofore separated components.
The foregoing object of this invention is achieved by providing a bag formed of flexible plastic material which defines an interior enclosed space, which interior space is vented to the outside of the bag to permit gaseous by-products of the foaming reaction to escape. A packet or pouch having a plurality of compartments therein, separated from each other by at least one frangible seal and having another frangible seal between the compartments in the packet and the enclosed space within the bag, is provided within the bag. First and second foam precursor components are contained in the separate compartments within the packet and are maintained separated by the interior frangible seal. The packet is formed of a barrier material which is capable of maintaining the foam precursors in a substantially stable and unreacted state for the desired shelf life of the foam-in-bag packaging system.
A packaging system of this type is disclosed in the co-pending application, Ser. No. 09/042,444 filed Mar. 13, 1998 entitled xe2x80x9cFoam In Bag Packaging System and Method For Producing the Same,xe2x80x9d which application is commonly assigned to the Assignee of this application and is incorporated herein by reference.
In accordance with a first preferred embodiment, the frangible seals of this invention, include a seal pattern which comprises one or more substantially continuous seal lines, each of which extend substantially between opposite sides of the packet to substantially divide the packet into a plurality of compartments. Each seal line is configured such that any imaginary straight line between the opposite sides of the packet and intersecting the seal line subtends at least one converging pocket defined by two segments of the seal lines which converge upon each other in the opening direction. Accordingly, the converging seal line segments are at oblique angles to the first direction. Preferably, this seal line defines a plurality of converging pockets which are spaced apart and extend substantially from one side of the compartment of the packet to the other. Thus, when the compartment is compressed, it causes liquid in the compartment to advance in the second direction, the leading edge or front of the liquid intersects a given seal line and liquid enters the wide end of each of the converging pockets and flows to the narrow end thereof. Fluid forces acting outwardly on the opposing panels which are joined along the converging seal line segments accordingly cause progressive peeling apart of the barrier material in the region of each converging pocket from the wide end toward the narrow end thereof.
By way of example and not by way of limitation, seal patterns in accordance with the first preferred embodiment of the invention include grids of spaced-apart intersecting seal lines in orthogonal or non-orthogonal fashion running oblique to the first direction and extending to each of the opposite sides of the packet, such that seal lines extending from one side to the other are defined by joined segments of the grid lines. Alternatively, the seal pattern may comprise wave form seal lines, such as saw-tooth or wavy lines extending from one side to the other. The converging pockets may take a variety of forms, including but not limited to triangular or V-shaped, cusp-shaped, U-shaped or other shapes.
In accordance with a second preferred embodiment of the invention, the seal pattern comprises a plurality of discrete sealed areas separated from one another by unsealed areas and arranged in a regular matrix having a density of at least about 15 matrix lines per inch, and more preferably at least about 50 matrix lines per inch.
A frangible seal in accordance with the invention may be formed by various techniques. In a preferred method, the opposing panels of barrier material have inner surfaces that are heat sealable to each other. One of the opposing regions of the inner surfaces that are to be joined to create the frangible seal is covered by a layer of resist material which prevents the heat sealing of the opposing surfaces to each other. The resist material is applied in a reverse image of the seal pattern. For example, to produce a square grid seal pattern, resist material is applied in a checker board pattern with the squares of resist material spaced apart such that the spaces between the squares define intersecting or orthogonal lines along which the panels of barrier material are to be joined.
The opposing panels of barrier material are overlayed with their inner surfaces confronting each other. The panels are pressed together and heat and pressure are then applied to the panels in a region of the resist material to cause heat sealing of the panels together in the areas not covered by the resist material.
The resist material may be applied by various techniques. In a preferred method, a resist material is printed onto the inner surface of one of the panels by a rotary printing press, such as a flexographic, roto-gravure or rotary letterbox press. Where the frangible seal is formed by a matrix of sealed areas, the seal advantageously is formed by printing resist material onto the inner surface of one of the panels by a half-tone printing process. The resist is applied with a half-tone dot line density of at least about 15 lines per inch and a surface coverage of at least about 60%.
The resist material may comprise a material having an acrylic/styrene resin-based vehicle, and other components, such as surfactants, alcohol, defoamers, and waxes may be added to the vehicle to improve adhesion, wetting out, and other properties of the resist for insuring accurate application of the resist pattern to the panel surface. A pigment may be added to the vehicle to facilitate visual inspection of the resist pattern. Also, solvent based inks, such as nitro-cellulose, polyamide type inks, may be used.
In accordance with one preferred embodiment of the invention, the inner surfaces of the panels are formed of a substantially non-polar polymer material which has not been treated by chemical modification, such as corona discharge treatment or flame treatment or by other treatments, to impair to any significant degree the strength of the non-frangible best seals. The panels are thus more readily heat sealable to each other so that sufficiently strong non-frangible seals may be achieved to form fluid-tight compartments in a packet. The invention also provides packets incorporating one or more frangible seals in accordance with the invention. In accordance with a preferred embodiment of the invention, a packet is provided having two compartments for containing two different components, the compartments being separated by a frangible seal according to the invention. Preferably, the packet also includes a second frangible seal between one of the compartments and the outside which, once the packet is placed in the bag, will comprise the interior space within the bag. Advantageously, the second frangible seal has a greater peel strength than the first frangible seal so that the second seal is not inadvertently ruptured when the user compresses one of the compartments to break the first seal, thus assuring that the two reactive fluids are brought into intimate contact within the package so that thorough mixing occurs before either fluid can escape the packet.
A further preferred embodiment of a packet for containing foam-forming precursors includes panels formed of a laminate having, from an outer layer to an inner layer thereof, an oriented polyethylene teraphthalate layer, a polyethylene tie layer, a metal foil layer, an ethylene acrylic acid layer and a non-polar polymer layer, such as low density polyethylene, linear low-density polyethylene, or the like.